SQL question: checking all required items
Hi all,
Given the following tables -
create table people (
person_id text primary key,
person_name text,
[...etc...]
);
create table items (
item_id text primary key,
item_name text,
is_required boolean,
[...etc...]
);
create table items_for_people (
person_id text,
item_id text,
primary key (person_id, item_id),
foreign key person_id references people(person_id),
foreign key item_id references items(item_id)
);
- how can I find those people who don't have _all_ of the items which
are marked "required"?
In other words, how do I select those rows in "people" which don't have
a corresponding row in "items_for_people" for *each* row in "items"
which has is_required=true?
Many thanks,
Ray.
---------------------------------------------------------------
Raymond O'Donnell, Director of Music, Galway Cathedral, Ireland
rod@iol.ie
---------------------------------------------------------------
On 8/10/07, Raymond O'Donnell <rod@iol.ie> wrote:
- how can I find those people who don't have _all_ of the items which
are marked "required"?In other words, how do I select those rows in "people" which don't have
a corresponding row in "items_for_people" for *each* row in "items"
which has is_required=true?
Without writing the exact query you need, I'll give you a couple of
ways to solve the problem of finding things in one set that aren't in
another.
select table1.id from table1 left join table2 on (table1.id=table2.id)
where table2.id is null
OR
select table1.id from table1 where table1.id is not in (select id from table2);
On 10/08/2007 21:29, Scott Marlowe wrote:
select table1.id from table1 where table1.id is not in (select id from table2);
Duh! I should have thought of that.... thanks for that, and apologies
for the stupidity (blame it on the glass of wine I had with dinner!).
Ray.
---------------------------------------------------------------
Raymond O'Donnell, Director of Music, Galway Cathedral, Ireland
rod@iol.ie
---------------------------------------------------------------
On 8/10/07, Raymond O'Donnell <rod@iol.ie> wrote:
On 10/08/2007 21:29, Scott Marlowe wrote:
select table1.id from table1 where table1.id is not in (select id from table2);
Duh! I should have thought of that.... thanks for that, and apologies
for the stupidity (blame it on the glass of wine I had with dinner!).
It's only obvious after you've done it a few times...
Show us the query when you're done, I'm sure there are enough folks
who'd like to see your solution.
?
Try
Select * from people where person_id in (
Select person_ID from Items_for_people group by Person_id Having Count(*) = (
Select count(*) from Items Where is_required = true))
Or something like that. That's the idea. Probe it and tell us.
(May be the sintaxis it's not correct, but I'm new in postgresql. In sql server it's ok)
________________________________
De: pgsql-general-owner@postgresql.org en nombre de Raymond O'Donnell
Enviado el: Vie 10/08/2007 03:07 p.m.
Para: 'PostgreSQL'
Asunto: [GENERAL] SQL question: checking all required items
Hi all,
Given the following tables -
create table people (
person_id text primary key,
person_name text,
[...etc...]
);
create table items (
item_id text primary key,
item_name text,
is_required boolean,
[...etc...]
);
create table items_for_people (
person_id text,
item_id text,
primary key (person_id, item_id),
foreign key person_id references people(person_id),
foreign key item_id references items(item_id)
);
- how can I find those people who don't have _all_ of the items which
are marked "required"?
In other words, how do I select those rows in "people" which don't have
a corresponding row in "items_for_people" for *each* row in "items"
which has is_required=true?
Many thanks,
Ray.
---------------------------------------------------------------
Raymond O'Donnell, Director of Music, Galway Cathedral, Ireland
rod@iol.ie
---------------------------------------------------------------
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
On 10/08/2007 22:03, Carlos Ort�z wrote:
Select * from people where person_id in (
Select person_ID from Items_for_people group by Person_id Having Count(*) = (
Select count(*) from Items Where is_required = true))
That seems to work fine! I'd only change "having count(*) = ..." to
"having count(*) >= ..." to allow for people having other items in
addition to the required ones.
Ray.
---------------------------------------------------------------
Raymond O'Donnell, Director of Music, Galway Cathedral, Ireland
rod@iol.ie
---------------------------------------------------------------
On 10/08/2007 21:42, Scott Marlowe wrote:
Show us the query when you're done, I'm sure there are enough folks
who'd like to see your solution.
Here's what I came up with:
select distinct ip.person_id from items_for_people ip
where exists (
(
select item_id from items
where is_required = true
)
except
(
select ip2.item_id from items_for_people ip2
inner join items i on (ip2.item_id = i.item_id)
where ip2.person_id = ip.person_id
and i.is_required = true
)
)
This finds all those who don't have all the required items, whatever
else they may have.
Comments and improvements are welcome!
Thanks for the help,
Ray.
---------------------------------------------------------------
Raymond O'Donnell, Director of Music, Galway Cathedral, Ireland
rod@iol.ie
---------------------------------------------------------------